In recent years the production of therapeutic antibodies has steadily increased and it is likely that therapeutic antibodies will become the biggest group of therapeutics available for the treatment of various diseases in the near future. The impact of therapeutic antibodies emerges from their specificity, such as the specific target recognition and binding function.
Antibodies can be obtained from an experimental animal that has been immunized with an immunogen. The immunogen is in most cases a polypeptide or a fragment of a polypeptide. To provide the immunogen in sufficient quantity and purity a recombinantly produced immunogen can be employed.
Generally prokaryotic and eukaryotic cells can be used for the recombinant production of polypeptides. The recombinant polypeptides can be obtained either in soluble form or as precipitate (inclusion body). Prior to chromatographic purification the insoluble polypeptide contained in the inclusion bodies has to be solubilized.
Generally the immunogen is a synthetic or a peptidic or a recombinantly produced or a fusion or a chimeric or a support conjugated polypeptide. For immunization the immunogen can be administered either alone or in combination with an adjuvant, such as Freud's adjuvant.
Knappe, T. A., et al. (J. Mol. Biol. 368 (2007) 1458-1468) reported that the Flap-region of FKBP12 can be replaced by the IF domain of the structurally related E. coli chaperone SlyD. The chimeric FKBP12-SlyD fusion polypeptide has a 200-times increase peptidyl-prolyl-cis/trans isomerase activity compared to the isolated polypeptide.
The E. coli SlyD and FKBP12 (wild type and mutants C23A and C23S) can be recombinantly produced in E. coli in high yield in soluble form (Standaert, R. F., et al., Nature 346 (1990) 671-674).
FKBP derived from thermophilic organisms and E. coli SlyD can be used as chaperons in the recombinant expression of fusion polypeptides in E. coli (Ideno, A., et al., Appl. Microbiol. Biotechnol. 64 (2004) 99-105). The E. coli SlyD and FKBP12 polypeptides are reversibly folding polypeptides (Scholz, C., et al., J. Biol. Chem. 271 (1996) 12703-12707).
The amino acid sequence of the FKBP12 polypeptide comprises a single tryptophan residue at position 60. Thus, FKBP12 mutants can be analyzed for structural integrity simply by analyzing the tryptophan fluorescence (DeCenzo, M. T., et al., Protein Eng. 9 (1996) 173-180). A test for remaining catalytic activity of the FKBP12 mutant can be performed by determining the remaining rotamase activity (Brecht, S., et al., Neuroscience 120 (2003) 1037-1048; Schories, B., et al., J. Pept. Sci. 13 (2007) 475-480; Timerman, A. P., et al., J. Biol. Chem. 270 (1995) 2451-2459). It is also possible to determine the structural integrity of FKBP12 mutants by determining the FK506- or Rapamycin binding (DeCenzo, M. T., et al., Protein Eng. 9 (1996) 173-180).
McNamara, A., et al. (J. Org. Chem. 66 (2001) 4585-4594) report peptides constrained by an aliphatic linkage between two C(alpha) sites: design, synthesis, and unexpected conformational properties of an i,(i+4)-linked peptide.
Suzuki, et al. (Suzuki, R., et al., J. Mol. Biol. 328 (2003) 1149-1160) report the three-dimensional solution structure of an archaic FKBP with a dual function of peptidyl-prolyl-cis-trans isomerase and chaperone-like activities. Expression vector, host, fused polypeptide, process for producing fused polypeptide and process for producing protein are reported in EP 1 516 928. Knappe, T. A., et al., reports that the insertion of a chaperone domain converts FKBP12 into a powerful catalyst of protein folding (J. Mol. Biol. 368 (2007) 1458-1468). A chimeric fusion polypeptide with superior chaperone and folding activities is reported in WO 2007/077008. In WO 03/000878 the use of FKBP chaperones as expression tool is reported. In EP 1 621 555 an immunogen, composition for immunological use, and method of producing antibody using the same are reported. Rebuzzini, G. (PhD work at the University of Milano-Bicocca (Italy) (2009)) reports a study of the hepatitis C virus NS3 helicase domain for application in a chemiluminescent immunoassay.
In WO 2007/077008 chimeric fusion proteins with superior chaperone and folding activities are reported. The conversion of FKBP12 into a powerful catalyst of protein folding by insertion of a chaperone domain is reported by Knappe et al. (Knappe, T. A., et al., J. Mol. Biol. 368 (2007) 1458-1468).